In the area of semiconductor technologies, the degree of integration of integrated circuit (ICs) becomes increasingly high with the advancing of large scale IC to ultra large scale IC. However, the static power consumption of an IC increases as a result of transistor short-channel effects due to the high degree of IC integration. Generally, static power consumption refers to power consumption required by a stable circuit, which includes power consumption at work conditions and in a standby mode. For a normal functioning transistor, the threshold voltage is fixed. When the transistor functions steadily, the current between source/drain is Ion. When the gate voltage cannot reach the threshold voltage, the current between source/drain is Ioff, and the transistor is in a standby mode. It is desirable to reduce the power consumption of the transistor in the standby mode to reduce the static power consumption of the transistor.
Conventional solutions to reduce static power consumption include modulating transistor threshold voltage using DG-FinFET (i.e., double gate-FinFET).
DG-FinFET is also known as four-terminal-FinFET or 4T-FinFET. FIG. 1 depicts a 4T-FinFET including 4 terminals a source end 12′, a drain end 13′, a first gate 14, and a second gate 15 on the sides of the fin. The first gate 14 and the second gate 15 are also respectively referred to as a drive gate and a control gate, each independently controlled by a voltage. The drive gate can be used to turn on or off devices while the control gate can be used to modulate the threshold voltage (Vt) of a transistor. Specifically, if the transistor is to be turned on, the control gate is used to reduce the threshold voltage, which leads the voltage of the drive gate to reach the threshold voltage to turn on the transistor. To put the transistor in a standby mode, the control gate is used to increase the threshold voltage, which leads the voltage of the drive gate not to meet the threshold voltage to switch the transistor in to the standby mode. When in a standby mode, as the threshold voltage increases, Ioff reduces. The power consumption in the standby mode decreases. Therefore, the static power consumption of the transistor can be reduced by controlling the control gate to increase the threshold voltage in the standby mode.
FIG. 2 shows a conventional three-terminal FinFET (3T-FinFET) including three terminals: a source end 12, a drain end 13, and a gate 11. The gate 11 is formed across a fin (not shown). The 4T-FinFET shown in FIG. 1 may be obtained through chemical mechanical polishing of the convex part of the upper gate of the fin of the 3T-FinFET. However, it is difficult to simultaneously produce a 3T-FinFET and a 4T-FinFET on a same wafer.